Lubricant loss or foreign material entry around the outside diameter of a seal element or housing closure is generally accomplished by having a tight, close fit between the contacting parts. Such a fit, however, does not allow the entire seal to move radially or float in order to accommodate shaft misalignment. Shaft misalignment here is accomodated by deflection or movement of the shaft lip sealing element. The amount of misalignment that can be accomodated then is limited by the deflection capabilities of the lip.
Another means of allowing the seal to accommodate shaft misalignment is to provide a loose or clearance fit between the outside diameter of the seal element and the housing in which it is mounted. This allows the entire seal element to move or float radially to accomodate shaft misalignment and relieves the strain from the shaft lip. If the seal has a clearance fit oil or the grease which has become liquid will readily escape from the housing. Additionally, shaft rotation provides centrifugal forces to such lubricant that tends to cause the lubricant to flow radially outward and if a loose fitting outside diameter is used, then lubricant will be forced out beyond the seal.
A means of allowing the seal to float or move radially and still prevent lubricant from being forced out around the seal has been developed.